diuretics

Question 1

Thiazides

- hydrochlorothiazide, chlorthalidone, indapamide

Answer 1

indicated for HTN, oedema, nephrogenic diabetes insipidus, contain sulfonamide

mechanism: moderately potent diuretic
- inhibit Na/Cl receptors in proximal DCT, prevent reabsorption of Na+ CL, produce a increase K excretion

SE:
CI in severe renal impairment/ anuria
Gout - diuretic-induced rise in serum uric acid concentration may precipitate gout (increase risk if high dose)

use low dose like 25mg then high, as high has more metabolic adverse effect

SE: dizzy, weak, muscle cramp, hypotension, hypontreamia, hypokalaemia, hypomg, dyslipidaemia, jaundice (nothing common)

Question 2

Amiloride

Answer 2

it is a potassium sparing diuretic (weak), inhibit Na channel in distal tubule reduce urinary K excretion

SE:
hyperkalaemia, hyponatremia*

CI:
in renal failure, as renal impairment increase risk of hyperkalaemia,

Question 3

spironolactone

Answer 3

mechanism: aldosterone antagonist inhibit Na absorption in distal tubule reduce K excretion

indication”: improves outcome in HF, use with ACEI, loop diuretic, digoxin in severe HF, monitor K every week then months

SE:
hyperkalaemia, hyponatraemia, gynaecomastia, menstrual irregularities

CI in renal failure, avoid in severe impairment (increase risk of hyperkalamia),

Pt with cirrhosis, spironolactone may precipitate if metabolic derangement occurs: renal failure, hyperchloraemic metabolic acidosis (associated with hyperkalaemia), hepatic encephalopathy

Question 4

acetazolamide (diamox)

Answer 4

indicated for glaucoma, seizures, benign intracranial HTN, altitude sickeness, diuretics

Mechanism: carbonic anhydrase inhibitor forces kidney to excrete HCO3, cause H and Cl retention act on proximal tubule

SE: metabolic acidosis, parasthesia, taste alteration, phosphate kidney stone

CI in pregnancy, SCA (sickle cell anaemia?), liver/ renal disease

Question 5

ADH - antagonist

- demeclocycline

Answer 5

antagonises the effect of antidiuretic hormone on renal tubules, promote excretion of free water, use in SIADH (sydrome of inappropriate antidiuretic hormone secretion) resistant to fliud restirction and high salt intake

Question 6

Frusemide - lasix

Answer 6

Loop Diuretics, contain sulfonamide

Indication: oedema* for HF, hepatic cirrhosis, renal impairment and nephrotic syndrome/ severe hypercalcaemia

CI in pregnancy (category C - cause fetal electrolyte disturbances, neonatal thrombocytopenia)

Mechanism:
inhibit reabsorption of Naand Cl in ascending limb of loop of Henle, works on Na/K/Cl exchange (20% of filtered Na potent, rapid, intense diuresis)

SE:
hyponatremia, hypokalaemia, hypomagnesaemia, dehydration, hyperuricaemia, gout, hypocalcaemia, deafness(espcially with rapid IV administration) more common, may impair renal function (if tx with nephrotoxic drugs increase risk of nephrotoxcity)

Use in combination with ACEI in HF,monitor fluid status, electrolyes